1. Field of Invention
An apparatus for aligning and supporting pipe or other tubular members during assembly and welding of confronting ends of the tubular members.
2. Description of the Prior Art
In the assembly of pipe and tubes, and in particular the assembly of sections of pipe and tube to elbows and tee fittings, one of the most important requirements for an acceptable product is proper finish, overall dimensions and true angular relationships between the abutting members to be welded. Prior art methods, fixtures and apparatuses required squares, leveling devices and clamping of the parts, together with tension bars that traversed the plane of weldment, in order to align and prevent movement due to expansion and shrinkage during the welding process. Prior art methods of assembly were also very time-consuming. It is estimated that approximately 75% of the time was devoted to set-up with 25% being devoted to actual welding time. In addition, a finish check for dimensional accuracy required manually held tape measure readings.
Further, secondary parts, such as couplings, nipples and gauge parts required application particular to the axial centerline of the pipe or tube by means of a combination square and sightglass level bars. Obviously, this allowed for considerable human error and was very time-consuming.
Various prior art aligning and clamping devices are exemplified by several U.S. patents. These include clamping chains, as shown in the Creek U.S. Pat. No. 3,881,715. It will be appreciated that chain grips are adjustable for pipes of varying diameter. However, these fixtures still require additional precise aligning techniques and, in the case of very accurate alignment, other auxiliary devices must be used for leveling and squaring of confronting tubular members.
Two U.S. patent references disclose clamping means for internally supporting adjoining members to be welded. Patent disclosures teach the provision of an unobstructed path for use with welding machines, but are relatively complex to assemble and do not provide the structural support required for accuracy in welding techniques. The Dearman U.S. Pat. No. 4,463,938 has particular application in field welding of relatively large pipe members and provides expandable internal clamping members for retaining each of the confronting pipes in alignment during welding. The Roddy U.S. Pat. No. 4,405,075 discloses a fixture with an expandable section positioned opposite the junction of two pipe ends to be welded. Although this provides rigid axial alignment for welding, there is no disclosure of an external support for the joined and retained members.
Other examples of clamping fixtures are illustrated in several patents granted to Timothy C. Dearman; namely, U.S. Pat. Nos. 3,653,574; 3,901,497; 3,944,202; 4,338,712; 4,356,615 and 4,623,085. Although the various Dearman clamping devices provide means for retaining pipe sections in confronting relationships, most of the clamping devices disclosed elongated bars which traverse the junction of the pipe members to be welded. This is satisfactory for manual welding, but it will be apparent that interference will be met with encircling welding machines utilizing orbital pipe or tube welding heads.
A further reference of interest is the Hilburn U.S. Pat. No. 3,596,898, which discloses a fixture for retaining the ends of tube pipe sections, wherein the fixture includes an upper and lower clamp again, extending across the junction to be welded.